First, I believe that the vu meter mod should de done. It looks gorgeous ! just make sure that this has no consequences on the clarity of the signal...

- will do my best, a small interface has to be provided (4 germanium diodes, 1 resistor, 1 small capacitor perchannel + one switch (Average / Peak), so the connection to the signal has about 3KOhm.

Powersafe mode : I see that there are some long cables (to go to the Switch and to come back) coming from the pins of the tube. Are you sure that this do not alter tha sound ?

- the wires are following the same path as the exsisting power lines, the switch only connects or disconnects a static voltage of 1.4 volt to pin 1 of the dl92, so switchted on, no change to before, switched off - just no current floating.

DAC ? Will it be internal ? Which one have you choosed ?

- formfactor, sound quality, price/performance ratio - HRT microstreamer DAC - a small little box i will provide an internal slot and two connectors for, could be removed and externally used at any time, fully powered by USB. an alternatiy would be the meridian explorer with 24bit 192 Khz, but a windows driver would be needed, not that universal and usable in the office with no right to install drivers.

Question: what is the benefit of having balanced input and balanced output is the internal design is NOT balanced ??

- a four pin mini xlr firstly is much better than a normal 3.5mm stereo jack. that you can connect a balanced source is a add-on. balanced equipment was primary designed for studio use with long cables because much better resistance against rf and other interferences. i think a double mono design is half way to balanced, only one amplifier per channel, but better channel separation as with one power supply and ground for both channels.

- a 4 pin xlr jack for headphone out makes sense, as this is the way the signals come out of the tu-05, two output transformers. also if you use a normal 3 pin stereo 6.3mm jack, you have to connect ground to ground, and then you have a connection between both amp parts. also it is the most universal connector. at the moment i am thinking of saving space by providing xlr to 2 speakers / 4 jacks and xlr to 6.3mm headphone out adapter cables instead of different jacks.

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Anyway, I love the project and believe that all the rest is for me very good ideas, including the XLR headphone plugs that offer better contacts and rigidity than a JACK.

- what i forgot but will look if and think that the standard transformer output could also be used as preamp out, it makes no sense to implement an preamp out after the df91 stage as both df91 and dl92 stage together make this great tu-05 sound.

i think the philco has more of this philips sweetness and magic, also more realistic sounding and slightly wider and deeper soundstage, but letś give the rca's some burn-in time until my second philco set arrives.

the rca is definetely better sounding (for my taste) than the tugsram dl91, telefunken dl92, lorenz dl92, tung-sol mil spec dl92 and orion 3s4t i also tested with the rft df97 after one of the philcos was damaged.

Just purchased an immaculate matched (both technical and date) Ken Rad's from the same seller I purchased the Raytheons from. I want to try an all American set up and until these Ken Rad's arrive I will make do with the Mil spec Sylvania's

But when the Ken Rad's arrive with the Raytheons I will have a complete set of matched technically and by date tubes in my amp and will report the results. The Ken Rad's like the Raytheons are war years NOS military stock.
Also, my amp was mailed on Saturday ( Sunday in Japan) and was marked as having left Japan on Sunday(my Sunday!) and for the first time since that notification it was updated this morning as now going through customs here in Canada.. They must be using Wilber and Orville Wrights flying machine to deliver mail between Japan and Canada!

So, hopefully customs will release it quickly and it goes out for delivery tomorrow, otherwise I will have to wait for Monday as the useless Canada post do not work weekends!

Just purchased an immaculate matched (both technical and date) Ken Rad's from the same seller I purchased the Raytheons from. I want to try an all American set up and until these Ken Rad's arrive I will make do with the Mil spec !